1. Field of the Invention
The present invention relates to a process cartridge, and an image forming apparatus which is capable of receiving the process cartridge mounted thereto.
The image forming apparatus may be an electrophotographic copying machine, a laser beam printer, an LED printer, or a facsimile machine.
2. Description of the Related Art
With reference to FIG. 12, a process cartridge, which can be detachably mounted to an image forming apparatus, is a unitary structure in which an image carrying member 51, a corona charger 52, a developing unit 53, a cleaning unit 54, and so on are incorporated in a single housing 55. The housing 55 has an opening 56 for an exposure operation and an opening 57 for a preexposure operation on the front and rear sides of the corona charger 52, respectively.
In recent years, a so-called contact charging method has been used to charge the photosensitive layer of the image carrying member. In this method, a voltage, which may be a d.c. voltage of 1 to 2 kilovolts or a voltage obtained by superimposing a d.c. voltage on an a.c. voltage, is applied from a power source to a conductive member, and this conductive member is brought into contact with the surface of the image bearing member so as to charge the surface of the image bearing member to a predetermined potential. Various contact charging methods, including the roller charging method, the blade charging method, the charging/cleaning method, and the brush charging method, have been proposed.
However, the conventional contact charging method in which the applied voltage contains an alternating component has a disadvantage in that a charging member, such as a roller, and the image bearing member vibrates at a frequency 2f, which is twice an alternating frequency f, or at a frequency which is an integral multiple of the frequency 2f due to the Coulomb's force, which acts between the image bearing member and the charging member, thus making the image bearing member or the like vibrate at 2f or a harmonic frequency thereof.
Also, a cleaning blade for removing toner on the image bearing member after image transfer is in contact with the image bearing member. Thus, vibrations inherent in the cleaning blade are generated between the image bearing member and the cleaning blade due to a frictional force on the contact surface between the image bearing member and the cleaning blade, vibrating the image bearing member and, generating noise having a frequency inherent to those vibrations and harmonic frequencies thereof.
Further, the vibrations of the charging member, the cleaning blade, and the image bearing member due to charging or the cleaning process cause the frame of a process cartridge to resonate, which in turn causes the frame of the image forming apparatus body to resonate and generate secondary noise.
This noise deteriorates the image quality.